In loudspeaker devices, including a loudspeaker, a housing and a resonance space, gas adsorbing materials—in the following referred to as sorber—like e.g. activated carbon or zeolite may be placed therein to improve sound generation of the loudspeaker device. A sorber in the resonance space of the loudspeaker leads to an apparent virtual enlargement of the resonance space by gas adsorption and desorption. The resonance frequency of the loudspeaker device is thereby lowered to a value that can be achieved without sorber only with an essentially larger resonance space.
However, it turned out that the use of sorbers bears several problems. One problem is the aging of the sorber in particular by irreversible adsorption of substances with high vapour pressure.
EP 2 003 924 A1 relates to a loudspeaker system in which a gas adsorber, obtained by adding a binder to a porous material including a plurality of grains so as to perform moulding, is used to physically adsorb a gas in a closed space of the speaker system. The porous material may be made of one selected from the group consisting of an activated carbon, zeolite, silica (SiO2), alumina (Al2O3), zirconia (ZrO3), magnesia (MgO), iron oxide black (Fe3O4) molecular sieve, fullerene and a carbon nanotube. The binder may be one of a powdery resin material and a fibrous resin material.
In view of the above-described situation, there exists a need for an improved technique that enables to increase the virtual acoustic volume of a resonance space of a loudspeaker device while substantially avoiding or at least reducing one or more of the above-identified problems.